83 lines
1.5 KiB
C++
83 lines
1.5 KiB
C++
#pragma once
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#include "config.h"
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#include <map>
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#include <unordered_set>
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#include "types.hh"
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namespace nix {
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/* Symbol table used by the parser and evaluator to represent and look
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up identifiers and attributes efficiently. SymbolTable::create()
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converts a string into a symbol. Symbols have the property that
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they can be compared efficiently (using a pointer equality test),
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because the symbol table stores only one copy of each string. */
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class Symbol
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{
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private:
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const string * s; // pointer into SymbolTable
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Symbol(const string * s) : s(s) { };
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friend class SymbolTable;
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public:
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Symbol() : s(0) { };
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bool operator == (const Symbol & s2) const
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{
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return s == s2.s;
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}
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bool operator != (const Symbol & s2) const
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{
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return s != s2.s;
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}
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bool operator < (const Symbol & s2) const
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{
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return s < s2.s;
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}
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operator const string & () const
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{
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return *s;
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}
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bool set() const
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{
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return s;
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}
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bool empty() const
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{
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return s->empty();
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}
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friend std::ostream & operator << (std::ostream & str, const Symbol & sym);
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};
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class SymbolTable
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{
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private:
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typedef std::unordered_set<string> Symbols;
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Symbols symbols;
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public:
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Symbol create(const string & s)
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{
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std::pair<Symbols::iterator, bool> res = symbols.insert(s);
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return Symbol(&*res.first);
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}
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unsigned int size() const
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{
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return symbols.size();
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}
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size_t totalSize() const;
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};
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}
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